/Engine/Source/Runtime/AVEncoder/Public/AudioTypes.h
The undecoded audio byte buffer is not guaranteed to be available after callback finishes. The pointer of the decoded audio sample buffer should be valid until the next decode call will happen.
typedef [TFunction](API\Runtime\Core\GenericPlatform\TFunction)< void(const [FAudioByteBuffer](API\Runtime\AVEncoder\FAudioByteBuffer) &AudioBytes, const [FAudioSampleBuffer](API\Runtime\AVEncoder\FAudioSampleBuffer) &)> OnAudioDecodeCallback